In industries, conjugated diene-vinyl aromatic hydrocarbon block copolymers are usually utilized as major materials for adhesive compositions, and such adhesive compositions can be applied in, for example, tapes, labels and disposable soft articles such as diapers, feminine napkins, surgical dressings and the like for adhesion purposes.
U.S. Pat. No. 5,089,550 discloses a block copolymer composition, which comprises 50 to 85 wt. % of a conjugated diene-vinyl aromatic hydrocarbon di-block copolymer, and 15 to 50 wt. % of a vinyl aromatic hydrocarbon-conjugated diene-vinyl aromatic hydrocarbon tri-block copolymer. This block copolymer composition can be used for adhesive compositions.
U.S. Pat. No. 5,112,889 discloses a pressure-sensitive adhesive, which comprises an A-B-A block copolymer or an AB block copolymer in geometry of such as a tapered block copolymer or a radial block copolymer, wherein the A blocks are derived from styrene or alphamethylstyrene and the B blocks are derived from isoprene, butadiene, or the hydrogenated thereof.
U.S. Pat. No. 5,420,203 discloses a process for producing block copolymer compositions, which comprises anionically polymerizing at least one vinyl aromatic hydrocarbon and at least one conjugated diene to form a living block copolymer, coupling the living block copolymer by adding a coupling agent, and then decoupling the coupled block copolymer by heating.
U.S. Pat. No. 5,510,423 discloses a conjugated diene-vinyl aromatic hydrocarbon linear block copolymer A-B-C-D, wherein A and D represent predominantly vinyl aromatic hydrocarbon polymer blocks, B represents a predominantly conjugated diene polymer block, and C represents a tapered block of the conjugated diene present in the block B and the vinyl aromatic hydrocarbon present in the block D. In the tapered block of C, the number of the vinyl aromatic hydrocarbon gradually increases toward the block D. This linear block copolymer can be used in adhesive compositions.
U.S. Pat. No. 5,719,226 discloses a hot melt adhesive composition with low viscosity. The hot melt adhesive composition comprises a blend consisting of an unhydrogenated or hydrogenated styrene-diene tri-block copolymer, and an unhydrogenated styrene-isoprene di-block copolymer.
The afore-mentioned U.S. patents disclose adhesive compositions having block copolymers in various ingredients. The adhesive compositions can be formed with various properties in order to fit requirements for different applications. Normally for the adhesive applications, properties of initial tack, peel strength and holding power properties are very important. Therefore, when developing the application of adhesives, there is a need to provide an adhesive composition with improved properties of initial tack, peel strength and holding power.